Received-SPF: pass (google.com: domain of linux-kernel+bounces-178484-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
From: Yang Yang <yang.yang@vivo.com>
To: Alasdair Kergon <agk@redhat.com>,
	Mike Snitzer <snitzer@kernel.org>,
	Mikulas Patocka <mpatocka@redhat.com>,
	dm-devel@lists.linux.dev,
	linux-kernel@vger.kernel.org
Cc: Yang Yang <yang.yang@vivo.com>
Subject: [PATCH 4/5] dm: Avoid sending redundant empty flush bios to the same block device
Date: Tue, 14 May 2024 17:04:43 +0800
Message-Id: <20240514090445.2847-5-yang.yang@vivo.com>
In-Reply-To: <20240514090445.2847-1-yang.yang@vivo.com>
References: <20240514090445.2847-1-yang.yang@vivo.com>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0:
	=?us-ascii?Q?UrlzF9nCRUX71F9pnbrPJ9Xqj/xTGvEustcLkzqMkGAoNi6lyVTdJi+j8kAz?=
 =?us-ascii?Q?jofCKLH1NxTUB3bvKfG7tw6gWvHSca5jcGl9drksUw5tgNimJFcS8/2gEvvh?=
 =?us-ascii?Q?raJfUL/BktY8YL/UpnpXH6T1gI9LPwIYKORZhqUlL1g3wl6LATKZQMwF/Uj2?=
 =?us-ascii?Q?Pby0xPw3YW2t1YhO6rIqD3FrijW4gPVQ6RV89un1X6p+otvflpn+lopnyVgC?=
 =?us-ascii?Q?Q6eQ1WoHMZ4sJqdI06uKo5r5ay295v1MIJDh8VP0ZpGLVbbGHKTd45JDTdVr?=
 =?us-ascii?Q?VtIQaMJJZpISUUaKQOWAV0z8acq9GoUFa8dsky92uuPPEhiWpXbBbwJw/XLf?=
 =?us-ascii?Q?Y8P+TAmESBWOM+Kix2P7PxiMo4hpHAuxwmQkTmwwdSEkCdUmdIy7S9yvI2DR?=
 =?us-ascii?Q?MIEDJf3WFSi0+3gJ88SciDzpcAjaaDK7IQVI+fHq/G5+N1ycx7Qba7XxBrpd?=
 =?us-ascii?Q?gnge7oWtbdBHSig2C89C1qU9rPZrT4mLiHRd2ilUuW/jImKkvmZdf1TILLtz?=
 =?us-ascii?Q?BkeFOEz7P1pXci3zQBGu0uQwGcfnbcT4CFRvFMik3McPH3YiCdAnqU8if7X7?=
 =?us-ascii?Q?DzLFwg6M5L9CGJJ5DMLyBqUmTEirSFzJLwyzye//9Abq6LQSVqYosWkalpkD?=
 =?us-ascii?Q?mWAiafA7MKyNm3bAIqXsN21AhWOKMGbgaD464tLQt+VDoGHcPoqyXGA2fF+o?=
 =?us-ascii?Q?B55yQ9jrsgkvisidVQ4fITyypNka3HbsB0nP7tnNgTnGPtRJq2djxCSae4X5?=
 =?us-ascii?Q?1Pq7gTCOQH/58slFGLotiy99FqyWbtOETKv1x6fENFvXUoCShzc8NizUAyIH?=
 =?us-ascii?Q?uhoUBZlSCDRi0UkECKOedXeF5mCRy5q1oHVLXsugrVldDawAeopJ7gsv9Owt?=
 =?us-ascii?Q?c2tqcNVMOnjNgz/ZxFJWiELRLgoqNM6/5H/KENbdDrO03v49k0Sg4EghXAcU?=
 =?us-ascii?Q?PrLGiCie44dlAcxWEGLlmCsGmccBSTm5Zwqui6nAXkCsXRCRqaOFkjRtezgd?=
 =?us-ascii?Q?2JrHg+IEAj0YWvdbXPSXOsyLZimzFSd3PNOjPlEyxEXRlv1lEt0CJy1EyVbc?=
 =?us-ascii?Q?pirK/dS+4kChg1PZJFi6puC8U310C6lC15ZZ32LIhbCoo1ikoURE9pWfGqvo?=
 =?us-ascii?Q?z+ej7KPc8K0rnH4OAOneh33FHP29BVBPZFVQstMmmUey48aKlOvYvOKDes6d?=
 =?us-ascii?Q?pI1gDOfgjP7HpjrKFTFiA6YrRtxlqqivyhkgBWn7cw71ZG9f1prpr9c64TlC?=
 =?us-ascii?Q?KbpX8g4KdHtEbTiWRfm2Chu8U/ki8fvSoi7x8fwZXYV7cFZPFwecA07ZbW8F?=
 =?us-ascii?Q?JC+DTGu8X+vT1433lvb8G/WCEWA5m/r7D6LYyaw+hQijAYkrHiXWmAetO9Gl?=
 =?us-ascii?Q?LhdL4hFPQtRG5p31IFuizzwO7CVPLTqto0V0RD1RognSajkaTRhxdyQJyQpz?=
 =?us-ascii?Q?/S6lsjlfdpi8udZtUQ+9cbHZGJEaui+BMOtm3tz+PF/hPkIhKT37dIZhodE2?=
 =?us-ascii?Q?I0RAWarJOkBXm84/5BN3dkslxVxbn+nsN1tW8Rro8+OAotN4JKFEGk9x4ZOk?=
 =?us-ascii?Q?R0z1wltD5rxC0JnT/A29lkSAU1YIrMYKbtrfU2qE?=
X-OriginatorOrg: vivo.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 782f40a1-db33-4e00-54da-08dc73f511f7
X-MS-Exchange-CrossTenant-AuthSource: SEYPR06MB6398.apcprd06.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 May 2024 09:05:58.7054
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 923e42dc-48d5-4cbe-b582-1a797a6412ed
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: mYMua6HthxQQWn3FReyaHltBAVKlpESTVcV2G90rkhgSkS/BxjpxYfLLeoj1WEXg/rY3+zghPQoi3+k96BS4Cw==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PUZPR06MB6102

If the num_targets is greater than the number of dm_devs in the
dm_table's devices list, __send_empty_flush() might invoke
__send_duplicate_bios() multiple times for the same block device.
This could lead to a substantial decrease in performance when
num_targets significantly exceeds the number of dm_devs.
This patch ensure that __send_duplicate_bios() is only called once
for each dm_dev with different target type.

Signed-off-by: Yang Yang <yang.yang@vivo.com>
---
 drivers/md/dm.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 25215b93c3cf..9dbddc214084 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1561,6 +1561,7 @@ static void __send_empty_flush(struct clone_info *ci)
 {
 	struct dm_table *t = ci->map;
 	struct bio flush_bio;
+	struct dm_target *ti;
 
 	/*
 	 * Use an on-stack bio for this, it's safe since we don't
@@ -1574,10 +1575,21 @@ static void __send_empty_flush(struct clone_info *ci)
 	ci->sector_count = 0;
 	ci->io->tio.clone.bi_iter.bi_size = 0;
 
-	for (unsigned int i = 0; i < t->num_targets; i++) {
-		struct dm_target *ti = dm_table_get_target(t, i);
+	if (!t->flush_pass_around) {
+		for (unsigned int i = 0; i < t->num_targets; i++) {
+			ti = dm_table_get_target(t, i);
+			__send_empty_flush_bios(t, ti, ci);
+		}
+	} else {
+		struct list_head *devices = dm_table_get_devices(t);
+		struct dm_dev_internal *dd;
 
-		__send_empty_flush_bios(t, ti, ci);
+		list_for_each_entry(dd, devices, list) {
+			struct list_head *targets = &dd->dm_dev->targets;
+
+			list_for_each_entry(ti, targets, list)
+				__send_empty_flush_bios(t, ti, ci);
+		}
 	}
 
 	/*
-- 
2.34.1